pqc/external/flint-2.4.3/fmpz_mat/inv.c

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2014-05-18 22:03:37 +00:00
/*=============================================================================
This file is part of FLINT.
FLINT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
FLINT is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with FLINT; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2010-2011 Fredrik Johansson
******************************************************************************/
#include "fmpz_mat.h"
void
_fmpz_mat_inv_2x2(fmpz ** b, fmpz_t den, fmpz ** const a)
{
fmpz_t tmp;
_fmpz_mat_det_cofactor_2x2(den, a);
fmpz_neg(&b[0][1], &a[0][1]);
fmpz_neg(&b[1][0], &a[1][0]);
fmpz_init(tmp);
fmpz_set(tmp, &a[0][0]);
fmpz_set(&b[0][0], &a[1][1]);
fmpz_set(&b[1][1], tmp);
fmpz_clear(tmp);
}
int
fmpz_mat_inv(fmpz_mat_t B, fmpz_t den, const fmpz_mat_t A)
{
slong dim = A->r;
if (dim == 0)
{
fmpz_one(den);
return 1;
}
else if (dim == 1)
{
fmpz_set(den, A->entries);
fmpz_one(B->entries);
return !fmpz_is_zero(den);
}
else if (dim == 2)
{
_fmpz_mat_inv_2x2(B->rows, den, A->rows);
return !fmpz_is_zero(den);
}
else
{
fmpz_mat_t I;
slong i;
int success;
fmpz_mat_init(I, dim, dim);
for (i = 0; i < dim; i++)
fmpz_one(fmpz_mat_entry(I, i, i));
success = fmpz_mat_solve_fflu(B, den, A, I);
fmpz_mat_clear(I);
return success;
}
}